Industrial revolution brings us a drastic technological development and a fast economic growth and promotes our living of standard significantly, but it also has substantial impacts and damages to the nature. Global surface temperature is climbing gradually to result in a global surface warming phenomenon called “Greenhouse Effect” and caused by a massive quantity of carbon dioxide discharged into the atmosphere. Within the past 150 years, the concentration of carbon dioxide in the atmosphere increases by approximately 25%, and the annual average global temperature rises by 0.5° C. As to the causes of a substantial increase of concentration of carbon dioxide in the atmosphere, our consumption of petroleum fuels is a major cause, in addition to our continuous deforestations. As the world population increases rapidly and the industrial development advances drastically, people are facing a shortage of natural resources including food, energy, minerals and construction materials and an extreme pressure of the ecological environment deterioration. At present, countries all over the world aggressively seek substitute resources to slow down the consumption of natural resources, and prepare for the time when our resources are exhausted in the future. Substitute energies including water power, tide, wind, solar energy and biomass energy and substitute food including fungi, algae and insets are developed at a full speed.
Algae can absorb carbon dioxide through photosynthesis to produce useful constituents such as vitamins, amino acids, pigments, proteins, polysaccharides, celluloses, and fatty acids, etc. In addition, the algae have the advantages of fast growth, high utilization of solar energy, and good nutrition, and thus the algae have become a popular topic of the research of substitute resources. For instance, algae can be used as fodders and substitute food or an agent for processing excessive carbon dioxide, or even an agent for extracting oils from green algae and converting the oils into biodiesels.
Therefore, it is an important subject for scholars and researchers in the related field to quickly cultivate a massive quantity of algae. The algae cultivation primarily requires sufficient light, carbon dioxide and nutrients. To effectively utilize light energy in a cultivation process, we generally use a cultivation device or system to achieve a large light receiving area, a fully mixed cultivation liquid for letting the algae have an effective contact of lights, and allowing the algae to be uniformly in contact with carbon dioxide and nutrients. In addition, a fully mixed cultivation liquid allows the algae to produce oxygen efficiently and prevents the algae from attaching onto the surface of the cultivation device that may result in a low light transmission rate of the cultivation device.
In past decades, many algae cultivation apparatuses and methods were introduced. For instance, a pool type photosynthesis reactor was used at the early stage for cultivating algae, and the structure of the pool type photosynthesis reactor is a water pool having a depth of approximately 15˜20 cm, and ventilations are provided at the bottom of the pool to promote circulation and mixing. The photosynthesis reactors of this sort come with a simple structure, an easy manufacture and a low cost, but the mixed nutrients are not uniform, and the algae generally sink to the bottom of the pool, so that this structure is replaced by canal type photosynthesis reactor. In a canal type photosynthesis reactor, the cultivation liquid is flowing, and a turbulent current produced between the fluid and the channel walls can provide the effects of mixing the cultivation liquid and suspending the cells. Thus, the cell growth curve of a general channel type photosynthesis reactor is much better than that of the pool type photosynthesis reactor.
However, the aforementioned photosynthesis reactors are outdoor open systems, which have the advantages of a low cost and a capability for a large-scale cultivation, but they also have the disadvantages of a too-large area that may be contaminated by other organisms or dust and affected by the weather easily. Furthermore, carbon dioxide may be leaked easily. Thus, a close cultivation system was introduced later. At present, the close cultivation systems include fermentation tanks, pipe type photosynthesis reactors, sheet type photosynthesis reactors, and spiral pipe type photosynthesis reactors, etc. The spiral pipe type photosynthesis reactor is a pipe type photosynthesis reactor bent into a spiral shape, and thus it has a longer reaction path, and a longer distance for exchanging more fluids to assist algae to gain sufficient carbon dioxide in the photosynthesis reactor. In addition, the pipe type photosynthesis reactor also has a larger backlight area for maximizing the utilization of light. The close cultivation system has the advantages of providing an easy control of environmental factors, a good resistance to contamination, and a high cultivation density, but also has the disadvantages of incurring a high cost and an easy damage to pipes by earthquakes.
Therefore, it is the most important subject of the present invention to design and develop an algae cultivation apparatus having with the advantages of an easy manufacture, a low cost, a flexible operation, a high production efficiency and a 24-hour supply of light source as well as cultivating a massive quantity of required algae.